Poly(arylene ether) resin is a type of plastic known for its excellent water resistance, dimensional stability, and inherent flame retardancy. Properties such as strength, stiffness, chemical resistance, and heat resistance can be tailored by blending it with various other plastics in order to meet the requirements of a wide variety of consumer products, for example, plumbing fixtures, electrical boxes, automotive parts, and insulation for wire and cable.
Poly(vinyl chloride) is currently the commercial dominant material for flame retardant wire and cable insulation. However, poly(vinyl chloride) is a halogenated material. There is mounting concern over the environmental impact of halogenated materials, and non-halogenated alternatives are being sought. There is therefore a strong desire—and in some places a legislative mandate—to replace poly(vinyl chloride) with non-halogenated polymer compositions. Given the popularity of white-colored small appliances and personal electronic devices, there is also a particular need for white or off-white colored cable insulation compositions that retain their color after photochemical aging.
Recent research has demonstrated that halogen-free poly(arylene ether) compositions can possess the physical and flame retardant properties needed for use as wire and cable insulation. See, for example, U.S. Patent Application Publication Nos. US 2006/131050 A1 and US 2006/131052 A1 and US 2006/135661 A1 of Mhetar et al., US 2006/131053 A1 and US 2006/134416 A1 of Kubo et al., US 2006/131059 A1 of Xu et al., and US 2006/135695 A1 of Guo et al. However, the compositions disclosed in these references are difficult to formulate in a white or off-white color, or they exhibit insufficient thermal or photochemical color stability, or both. And, while the problem of photochemical yellowing of poly(arylene ether)-containing compositions has long been known, existing solutions to this problem are either ineffective or impractical for white and off-white wire and cable insulation. For example, in one approach, photochemical yellowing of the poly(arylene ether) is compensated for by the incorporation of a photobleachable dye. See, for example, U.S. Pat. Nos. 4,493,915 and 4,551,494 to Lohmeijer. This approach is not effective in white and off-white poly(arylene ether) compositions because the presence of the photobleachable dye is incompatible with the desired white or off-white color. In another approach, the surface of an article comprising a polyphenylene ether and a second resin is treated with solvent to selectively remove polyphenylene ether from the surface of the article. See, for example, U.S. Pat. No. 5,055,494 to van der Meer. This approach is impractical for wire and cable insulation because of the large surface area that would need to be solvent treated.
There therefore remains a need for white and off-white colored poly(arylene ether) compositions that exhibit the physical and flame retardant properties required for wire and cable insulation and further exhibit color stability after prolonged light exposure.